We have just got them, so are novices too. We got ours from a breeder in the local paper. A rescue centre I talked to the other day had baby g-pigs in, as well as adults.
You have to think carefully in advance whether you want boars or sows as it all seems a bit of a minefield. Boys are apparently OK together if they start off as babies, as are girls, but if a boar is allowed to mount a sow, or sometimes if they even see sows, the boars can start to fight each other. So, I don't think you can even keep neutered sows and boars together.
Sows should start with their first litter before they are one, or their bodies will be too inflexible to give birth (know the feeling!). They become sexually mature at something like 3-4 weeks, and will mount sisters/mother (ick!).
If you later try to mix them with rabbits, a male will often try to mate with them (whether they are boys or girls) and a female could kill them as they are very territorial.
There you go ... all I know about g-pigs! This is what the breeder has told me anyhow, though I get the impression she may have been over-cautious about some things (e.g. I am sure some people must keep boars and sows in separate cages without the boars fighting).